#include <misc.h>

static const u8 MD2_S[256] = {
    0x29, 0x2E, 0x43, 0xC9, 0xA2, 0xD8, 0x7C, 0x01, //
    0x3D, 0x36, 0x54, 0xA1, 0xEC, 0xF0, 0x06, 0x13, //
    0x62, 0xA7, 0x05, 0xF3, 0xC0, 0xC7, 0x73, 0x8C, //
    0x98, 0x93, 0x2B, 0xD9, 0xBC, 0x4C, 0x82, 0xCA, //
    0x1E, 0x9B, 0x57, 0x3C, 0xFD, 0xD4, 0xE0, 0x16, //
    0x67, 0x42, 0x6F, 0x18, 0x8A, 0x17, 0xE5, 0x12, //
    0xBE, 0x4E, 0xC4, 0xD6, 0xDA, 0x9E, 0xDE, 0x49, //
    0xA0, 0xFB, 0xF5, 0x8E, 0xBB, 0x2F, 0xEE, 0x7A, //
    0xA9, 0x68, 0x79, 0x91, 0x15, 0xB2, 0x07, 0x3F, //
    0x94, 0xC2, 0x10, 0x89, 0x0B, 0x22, 0x5F, 0x21, //
    0x80, 0x7F, 0x5D, 0x9A, 0x5A, 0x90, 0x32, 0x27, //
    0x35, 0x3E, 0xCC, 0xE7, 0xBF, 0xF7, 0x97, 0x03, //
    0xFF, 0x19, 0x30, 0xB3, 0x48, 0xA5, 0xB5, 0xD1, //
    0xD7, 0x5E, 0x92, 0x2A, 0xAC, 0x56, 0xAA, 0xC6, //
    0x4F, 0xB8, 0x38, 0xD2, 0x96, 0xA4, 0x7D, 0xB6, //
    0x76, 0xFC, 0x6B, 0xE2, 0x9C, 0x74, 0x04, 0xF1, //
    0x45, 0x9D, 0x70, 0x59, 0x64, 0x71, 0x87, 0x20, //
    0x86, 0x5B, 0xCF, 0x65, 0xE6, 0x2D, 0xA8, 0x02, //
    0x1B, 0x60, 0x25, 0xAD, 0xAE, 0xB0, 0xB9, 0xF6, //
    0x1C, 0x46, 0x61, 0x69, 0x34, 0x40, 0x7E, 0x0F, //
    0x55, 0x47, 0xA3, 0x23, 0xDD, 0x51, 0xAF, 0x3A, //
    0xC3, 0x5C, 0xF9, 0xCE, 0xBA, 0xC5, 0xEA, 0x26, //
    0x2C, 0x53, 0x0D, 0x6E, 0x85, 0x28, 0x84, 0x09, //
    0xD3, 0xDF, 0xCD, 0xF4, 0x41, 0x81, 0x4D, 0x52, //
    0x6A, 0xDC, 0x37, 0xC8, 0x6C, 0xC1, 0xAB, 0xFA, //
    0x24, 0xE1, 0x7B, 0x08, 0x0C, 0xBD, 0xB1, 0x4A, //
    0x78, 0x88, 0x95, 0x8B, 0xE3, 0x63, 0xE8, 0x6D, //
    0xE9, 0xCB, 0xD5, 0xFE, 0x3B, 0x00, 0x1D, 0x39, //
    0xF2, 0xEF, 0xB7, 0x0E, 0x66, 0x58, 0xD0, 0xE4, //
    0xA6, 0x77, 0x72, 0xF8, 0xEB, 0x75, 0x4B, 0x0A, //
    0x31, 0x44, 0x50, 0xB4, 0x8F, 0xED, 0x1F, 0x1A, //
    0xDB, 0x99, 0x8D, 0x33, 0x9F, 0x11, 0x83, 0x14, //
};

static void MD2_iterate(MD2_t *_rest m) noexcept {
  byte h[48];

  byte t;
  int  j = m->c[15];
  for (int i = 0; i < 16; i++) {
    h[i]      = m->h[i];
    h[i + 16] = t = m->b[i];
    h[i + 32]     = (t ^ m->h[i]);
    j = m->c[i] ^= MD2_S[t ^ j];
  }
  t = 0;
  for (int i = 0; i < 18; i++) {
    for (int j = 0; j < 48; j += 8) {
      t = h[j + 0] ^= MD2_S[t];
      t = h[j + 1] ^= MD2_S[t];
      t = h[j + 2] ^= MD2_S[t];
      t = h[j + 3] ^= MD2_S[t];
      t = h[j + 4] ^= MD2_S[t];
      t = h[j + 5] ^= MD2_S[t];
      t = h[j + 6] ^= MD2_S[t];
      t = h[j + 7] ^= MD2_S[t];
    }
    t = (t + i) & 0xff;
  }

  *(v8u8 *)m->h       = *(v8u8 *)h;
  *(v8u8 *)(m->h + 8) = *(v8u8 *)(h + 8);
}

void MD2_init(MD2_t *_rest m) noexcept {
  if (!m) return;
  *m = (MD2_t){};
}

void MD2_input(MD2_t *_rest m, const void *_rest data, size_t len) noexcept {
  if (!m) return;
  for (size_t i = 0; i < len; i++) {
    m->b[m->p++] = ((const byte *)data)[i];
    if (m->p == 16) {
      MD2_iterate(m);
      m->p = 0;
    }
  }
}

const void *MD2_end(MD2_t *_rest m) noexcept {
  if (!m) return NULL;

  for (int i = m->p; i < 16; i++) //
    m->b[i] = 16 - m->p;
  MD2_iterate(m);

  for (int i = 0; i < 16; i++) //
    m->b[i] = m->c[i];
  MD2_iterate(m);

  return m->h;
}

const void *MD2_val(const MD2_t *_rest m) noexcept {
  if (!m) return NULL;
  return m->h;
}

void MD2_print(const MD2_t *_rest m) noexcept {
  if (!m) return;
  for (int i = 0; i < 16; i++) {
    printf("%02x", m->h[i]);
  }
  printf("\n");
}

const void *MD2(MD2_t *_rest m, const void *_rest data, size_t len) noexcept {
  if (!m) return NULL;
  MD2_init(m);
  MD2_input(m, data, len);
  return MD2_end(m);
}
